I have/had a friend, from my more non observant days, who I went to High School with many years ago. I don't see him often, but I saw him a few weeks ago. I was literally shocked at how offensive he was when talking about any Jewish topic of any kind. Reform Judaism in his childhood turned him into an anti-religious virtually self hating Jew today.

How does one react toward someone like this ?

One of the mitzvoim is Ahavat Yisroel, but how can we show it to someone who goes out of his way to hate everything related to Jewish identity ?